Sochi: With Spain unbeaten in 20 games and Portugal having lost one competitive match since September 2014, Friday's clash here appeared to be a case of an irresistible force meeting an immovable object - at least until Wednesday.
Then, in a drastic and sensational move, Spain fired coach Julen Lopetegui and replaced him with Fernando Hierro, whose only previous senior coaching experience was at second-tier Spanishc club Oviedo.
Lopetegui, who only last month extended his contract as Spain coach, agreed on Tuesday to take over at Real Madrid next season -- but the Spanish federation (RFEF) only found out five minutes before the official announcement and were furious.
contrast with Portugal and the manner in which their coach Fernando Santos agreed to renew his contract after winning Euro 2016 two years ago could not have been greater.
"We sat down, had a coffee and easily reached an agreement," he said at the time.
The neighbourly rivalry and the intriguing prospect of a duel between Real Madrid team mates Sergio Ramos of Spain and Portugal's Cristiano Ronaldo meant the Group B match was always going to be one of the highlights of the opening round.
Some teams can be galvanised by such episodes, however, and Ramos quickly issued a war cry on Twitter.
"We are the national team, we represent a badge, colours, a fanbase and a country," he said.
"Our responsibility and commitment is with you as well as for you. Yesterday, today and tomorrow together," he said.